Frequently Asked Questions
Q: How does an air-conditioner work?
A: Most people think that air conditioners lower the temperature in their homes simply by pumping cool air in. What’s really happening is the warm air from your house is being removed and cycled back in as cooler air. This cycle continues until your thermostat reaches the desired temperature. An air conditioner uses the evaporation of a refrigerant, like Freon, to provide cooling.
This is how the evaporation cycle in an air conditioner works: The compressor compresses cool Freon gas, causing it to become hot, high pressure Freon gas. The hot gas runs through a set of coils so it can dissipate its heat, and it condenses into a liquid. The Freon liquid runs through an expansion valve, and in the process it is evaporated to become cold, low-pressure Freon gas. The cold gas runs through a set of coils that allow the gas to absorb heat and then cool down the air inside the home. Mixed in with the Freon is a small amount of lightweight oil. This oil lubricates the compressor.
Q: How does a heat pump work?
A: If you have read “How does an air-conditioner work?”, then you are familiar with the basic process that allows an air conditioner to concentrate cold in one set of coils (inside the house) and heat in another set (outside the house).
Imagine that you took an air conditioner and flipped it around so that the hot coils were on the inside and the cold coils were on the outside. Then you would have a heater. It turns out that this heater works extremely well. Rather than burning a fuel, what it is doing is “moving heat.”
A heat pump is an air conditioner that contains a valve that lets it switch between “air conditioner” and “heater.” When the valve is switched one way, the heat pump acts like an air conditioner, and when it is switched the other way it reverses the flow of Freon and acts like a heater.
Heat pumps can be extremely efficient in their use of energy. But one problem with most heat pumps is that the coils in the outside air collect ice. The heat pump has to melt this ice periodically, so it switches itself back to air conditioning mode to heat up the coils. To avoid pumping cold air into the house in air conditioning mode, the heat pump also lights up burners or electric strip heaters to heat the cold air that the air conditioner is pumping out. Once the ice is melted, the heat pump switches back to heating mode and turns off the burners.
Q: Should I close the registers in rooms that are not used often?
A: No. Closing registers and shutting off rooms hinders the system’s designed airflow and greatly reduces its efficiency. If properly installed, each system is designed to cool a certain number of square feet. Contrary to popular belief, closing off registers and shutting doors does not save much energy. It causes the air conditioning system to cycle more often and work harder to cool less space.
Q: How important is adding a humidifier to my home’s heating system?
A: In the winter, air is drier. This dry air can damage the woodwork and furniture you have in your home, as well as zap the moisture from your skin. Dry air even makes you feel cooler because your body senses heat as a combination of temperature and humidity. Adding humidity to offset this drying process will improve your comfort as well as preserve the woodwork in your home. As an added benefit, you may actually be able to lower your thermostat a couple of degrees. You will not only feel warmer, but will actually lower your home heating bill.
Q: What size heating and air conditioning system do I need?
A: An oversized HVAC system will turn on, satisfy the thermostat and shut off before it can adequately remove sufficient moisture from the air. This problem is more physically noticeable during the cooling season because you feel cold (not cool) and the excessive moisture in the air causes you to feel damp and sticky. Failure to remove sufficient moisture from the air can also lead to property damage such as mold and mildew in the summer months and dry-rot in the winter months. What’s more, the stress of short-cycling (too many starts and stops) also greatly decreases the life of the system while greatly increasing your monthly energy bills.
On the other hand, a system that is too small cannot heat or cool adequately, especially in extreme weather conditions. The air conditioner will run constantly in the summer and the furnace will do the same in the winter. Once again, this problem will lead to decreased life span and increased energy usage.
A correctly sized heating and cooling system isn’t based on square footage alone. It’s based on structure. Many factors go into determining the size of the HVAC system including: the design of the house; materials used in the exterior walls; type and sizes of windows; insulation above, below and in the walls; basement and attic conditions; house orientation; and so on.
Q: What is the regular maintenance needed for my heating and cooling units?
A: We recommend that your heating and cooling system be tested and inspected twice a year: Once in the spring and once in the fall. This will ensure your heating and air system is operating safely and efficiently. We also recommend that you change your air filters regularly, depending on the type of filter you have. If you use the standard throw-away 1” filter, you should change it every 6-8 weeks. Don’t let the filter get clogged as this can cut down on efficiency and/or cause damage to the unit.
If you have a question you would like to ask, please feel free to call our Raleigh office at (919) 400-7790 or you can choose the “Ask-A-Tech” link located at the top of the page. We will have a technician review your question and contact you with a response.
